Motor-generator set



Feb. 2, 1932.

G. W. PIERCE MOTOR GENERATOR SET Filed April 23, 1928 Petented Feb. 2,i932 siren senses or memes,

stores-eminence sun ori ami s ments The present invention, besideshaving other fields of usefulness, relates more particularly to thecontrol of motor-generator sets.

The invention will be explained in connec- V tion with the accompanyingdrawings, in

to description may he found in application Serial No. 262,08t, filedJune 28, 192?, of which the present application is a division. The core2 may freely rest centrally upon a support 6, but is shown clumpedbetween the supso port 6 and a second clamping member 8. When onelectric current is passed through the coil, s= magnetic field will. beestablished that will cause mechanical distortion or deformation of thecore 2 by megnetostriction.

This action of the magnetic field upon the core 2 will, for brevity, behereinafter termed stimulation.

H the current or voltage is alternating, the electromagnetic fieldcrested thereby will also so be alternating. The core 2 will, therefore,in-

crease and decrease in length, let us say, many times e second, everyvariation in the current producing its stimuletive efiect on the core 2.The core 2 will, in consequence, freely vibrate mechanically bymsgnetostriction about u nodal point at its center with a period ofvibruti-on equal to the period of the alternating electromotive force.Ordinarily, these vibrutions will quite small. When the alteril notingfrequency is close to, or substantially the same as, the naturalfrequency of mechsnicsl vibration of the core 2, however, the em plitudeof vibration of the core, though still small, becomes relatively quitelarge. The

rod will then react inductively on the load to render its consumption ofpower critical as.

to frequency for frequencies near the free frequency of the rod. Themechanical damping of the rod, mounted as shown, is as small 59 aspossible, with the result that the resonant filed June so, 1822?, Eerie!Ho. 26.23%, and in (Senate December $1, 1927. bivlded and thisapplication filed April 28, 1928. Serial No. 272,031,

response of the rodis very sharp and pro nounced, Ofcourse, there willusually be more than one specific frequency of magnetization at whichthe rod will thus resonate; for, in addition to one or more naturalfundamental frequencies of mechanical vibration, it has also frequenciesof vibration determined by the operation of the rod in helves, thirds,fourths, fifths, etc. The theory of this operation is explained more atlength in the above-identified application, and it will be suficienthere to remember thet the operation described herein is uelly applicableto the fundamentals end to t eir overtones.

According to u feature of the present invention, the movements of themagnetostrictive device may be employed to efiect the operation of urelay 31. The electric currents traversing the core-driving coil 10produce variations of its magnetic field. The currents thus efiect msetizetion of the megnetostrictive core, en the letter becomesmagnetostrictively deformed, end vibrates. These deformations may verythe electrical conductivity of one or more microphones 15, 17 that areattached to the core 2, as described in the said cpplicutiomendillustrated in Fig. 3. In Fig. l, however, the microphones ure replacedby inertia switch armatures 39 and 4,1 hinged at 43 end yieldinglypressed against a. contect meber 4d at the end of the core 2 by aninsulated spring t5.

The vibration of the core tends to drive the inertia armature out ofcontact with the contact member 44;, and the s ring 45 tends to restorethe contact. As t e motion of the inertia, armature under the action ofthe spring is slow relative to the frequency oi vibration of the rod,the contsct is open for :1 large part of the time, causing a reductionin the current of the local circuit. Thereversible internal stressescaused by the mugnetostrictive deformations of the core may be made,therefore, to very the current in e coil 29 of u relay 31. The coil 29is in circuit with a local battery 11. A. motor-genorator set is shownwith the motor at 53 end the generator at 55. The coil 10 is connectedin circuit with the generator by the generator output conductors 12,14:, in parallel with the extra nerator 1oad'57. The contact members othe relay31 are connected in shunt to the motor field-Winding resistor59.

The operation will be further understood in connection with the curve ofFig. 2, in which the local current is plotted as the ordinate againstthe frequency of exciting current, as the abscissa, where microphones orresistance-varying elements are associated with the magnetostrictivecore. As the frequency of the exciting current in the coil 10 isincreased from a low value to a value ap proaching the natural frequencyotmechanica-l vibration of the core,-whether a fundamental or anovertone,-the local current throu h the contacting members 39, 41, orthe hie, decreases. For the operation of a relay, such as the relay 31,the device may 'be adjusted to trigger at, say, 30 milliamperes, asindicated at 63. The triggering of the relay will take place at afrequency F, as indicated in Fig. 2. The minimal point 61 of the curverepresents the resonant fre quency, or thetnatural frequency of freevibration of the core, whether a fundamental or an overtone. If desired,the relay-operating point may be chosen at the point 63, the point 61,the point 65, or elsewhere on I the current-frequency curve.

In connection with a motor-generator set, it is'preterable to have theoperation at the point 63. Then, when the speed of the motor 53 rises tosuch a value as to produce at the generator terminals and in the coil 101 a frequency of the value F, the resulting deformation of the core 2causes a. decrease in the current traversing the relay coil 29, so thatthe relay 31 will close, causing slowmg down of the motor. The generatorfrequency then begins to decrease, causing the relay contact to openand, consequently, speeding up the motor. The magnetostrictwo core withassociated apparatus thus controls the speed of the motor-generator set.The same principle of control is obviously applicable to rotaryconverters and similar machinery.

Modifications will readily occur to persons skilled in the art, and allsuch are considered to fall Within the spirit and scope of theinvention, as defined in the appended claims.

- What is claimed is:

a 1. A motor-generator set having, in combination, two machines, namelya motor and a generator, meansmechanically connecting .the motor and thegenerator together, a vibrator connected with the motor and thegenerator, and means whereby the vibrator is deformed mechanically whenstimulated from one of the machines and causes variations in theelectric circuit of the other machine when deformed mechanically.

2. motor-generator set having, in combination, a motor and a generatormechani- -cally connected together, and magnetostrictive means connectedwith the motor and the generator for controlling the speed of the motor.

3. A motor-generator set having, in combination, a motor and a generatormechanically connected together, a speed-controlling rheostat for themotor, a magnetostrictive body, an energizing'coilfor the body incircuitwith the generator, a rela for shortcircuiting the rheostat and havingan energizing coll, means the electrical conduction of which varies inaccordance with the magnetostrictive deformations of the body, and meansconnecting the last-named means, the relay coil and the body intocircuit.

a. A motor-generator set having, in combination, two machines, namely amotor and a generator, means mechanically connecting the motor and thegenerator, together, means connected with the motor and the generatorfor controlling the speed of the'motor comprising a body adapted to bedeformed mechanically when stimulatedelectrically and to cause anelectric response when deformed mechanically, and means whereby the bodyis deformed mechanically when stimulated electrically from one of themachines and causes an electric response in the other machine whendeformed mechanically.

5. A motor-generator sethaving, in combination, two machines, namel amotor and a generator, means mechanica ly connecting the motor and thegenerator together, a speedcontrolling rheostat for the motor, meanscontrolled by the generator and adapted to be deformed mechanically whenstimulated electrically and to cause an electric response when deformedmechanically for short-circuiting the rheostat, and means whereb thefirstnamed means is deformed mechanically when stimulated electricallyfrom one of the machines and causes an electric response in the othermachine when deformed mechanically.

6. An electric system having, in combination, a vibrator comprising abody, means for exciting the body by reversible internal stressestherein, an electric circuit, means for varying the electricalconduction of the circuit responsive to the vibrations of the body,

a switch having an energizing coil connected in the circuit, and anelectric circuit in which the switch is connected.

7. An electric s stem having, in combine tion, a magnetostrlctive body,means for causing magnetostrictive deformations of the body, an electriccircuit in which the body is connected, means for causing the currentflowing in the circuit to var in accordance with the magnetostrictiveeformations of the body, a switch having an energizing coil eon- 1.nected in the circuit, and a circuit in which the switch is connected. I

8. A motorgenerator set having,combination, a motor and a generatormechanically connected together, a magnetostrictivevibra- -1 tor havingan energizing coil connected in circuit with the generator, means forcontrolling the motor, and means the electrical conduction of whichvaries in accordance with the magnetostrictive deformations of thevibrator connected in circuit with the motorcontrolling means.

9. A motor-generator set having, in combination, a motor and a generatormechanically connected together, a speed-controlling rheostat for themotor, a vibrator comprising a body, means controlled by the generatorfor exciting the body by reversible internal stresses therein, anelectric circuit the electrical conduction of which is varied inaccordance with the vibrations of the body, and a relay forshort-circniting the rheostat having an energizing coil connected in thecircuit.

10. A motor-generator set having, in combination, a motor and agenerator mechanically connected together, means for controlling themotor, a vibrator, means controlled by the generator for exciting thevibrator by reversible internal stresses therein, and means theelectrical conduction of which is varied in accordance with thevibrations of the vibrator connected in circuit with themotor-controlling means.

In testimony whereofll have hereunto sub scribed my name.

GEORGE W. PIERCE.

